Field of the Invention
This invention relates to safety valves for relieving excessive pressure in fluid systems to avoid equipment damage and personal injury. More specifically, this invention relates to valve components to improve valve performance in certain contemporary safety valve designs.
Pressure relief or safety valves are employed for over-pressure protection in operating systems that utilize fluids in either liquid, vapor, or gaseous states. Typical of such safety valves is a huddling chamber type valve which has been marketed for a number of years. Such valves include a nozzle for admitting fluids into the valve from a pressure vessel. A valve seat is formed on the discharge end of the nozzle in a chamber of the main body of the valve. The nozzle is closed to prevent fluid escape by a valve member generally referred to as a "valve disc" which is movable relative to the nozzle seat and biased to a closed position on the seat by a compression spring. When the fluid pressure in the vessel exceeds a predetermined value, the valve disc is forced from the nozzle seat to admit fluid from the pressure vessel into the valve chamber from which the fluid flows through an outlet leading from the chamber. When the pressure in the vessel drops to a predetermined level the compression spring forces the valve disc back on the nozzle seat closing the safety valve. The difference between the pressure at which the valve opens and the pressure at which the valve recloses is often referred to as "blowdown".
A valve of the general type of the present invention is illustrated and described in the following U.S. Pat. No. 4,036,250 for BLOW-DOWN SAFETY VALVE, issued to James W. Dashner, Jul. 19, 1977. More specifically, valves of the type of the present invention are 1900 SRV's and 1990 SRV's manufactured and marketed by Dresser Industries, Industrial Valve Operation, Dresser Valve and Controls Division, and described and illustrated in a Dresser Industries Catalog published in 1991, entitled Safety Relief Valves, Sizing and Selection, Fall, 1991, SRV-1.